1. Field of the Invention
The present invention relates to an electronic device such as a crystal oscillator chip or a piezoelectric device and a manufacturing method thereof.
2. Description of the Related Art
Since a crystal oscillator has an excellent frequency characteristic, the crystal oscillator is widely used as a component to be mounted on a printed circuit board. However, in order to stabilize the characteristics of the crystal oscillator, the crystal oscillator is preferably received in a hermetic container to block the influence of external air. “GLASS-CERAMIC COMPOSITE AND FLAT PACKAGE TYPE PIEZOELECTRIC COMPONENT USING THE SAME” (JP-A-11-302034) is proposed as an example of such a package structure.
This package is characterized by that a package is constituted using a mixture of ceramics and glass powder, which have almost the same thermal expansion coefficient as a quartz crystal chip, in an electronic device in which the quartz crystal chip is placed on a base and the resultant is covered with a cap.
However, since this package is formed of a glass-ceramic composite, the package is manufactured by individual production of placing a quartz crystal chip on a base and covering the resultant with a cap and thus the productivity thereof is very low. In addition, it is difficult to process the glass-ceramic composite and thus the production cost thereof is high.
To solve this defect, a method of manufacturing a package out of glass which can be easily processed is proposed and an “electronic component package” or the like is proposed (JP-A-2003-209198).
The above-mentioned example will be described below with reference to FIGS. 12A to 12F. The example provides a method of manufacturing an electronic device 100 through the use of steps of (a) forming a through-hole in a base 110, (b) causing low-melting-point glass to flow into the through-hole and thrusting a metallic pin 120 thereinto, (c) processing a glass plate into a concave state while thrusting the metallic pin 120, (d) forming an electrode 130 by printing, (e) mounting a component such as a crystal oscillator on the metallic pin, (f) sealing and bonding a cap 160 and the base 110 with an encapsulant 150. In the step of (c), the metallic pin 120 closely fixed to the base 110 can be obtained by setting the heating temperature to the softening temperature of glass (about 1000° C.) or higher to weld the glass and thus the air-tightness can be maintained in the step of (f), thereby manufacturing the electronic device at a low cost.
In the step of (c) of the method of manufacturing the electronic device 100, there is a problem shown in FIGS. 13C-1 to 13C-3. FIGS. 13C-1 to 13C-3 are partially-enlarged sectional views illustrating the metallic pin in the step of (c). That is, as shown in FIG. 13C-1, when the metallic pin 120 is short or the thrust distance is small, the metallic pin 120 is covered with the low-melting-point glass 170. Accordingly, the electrical connection between the electrode 130 formed in the step of (d) and the metallic pin 120 is not guaranteed. As shown in FIG. 13C-2, even when the metallic pin 120 is thrust as designed, the glass may cover the tip of the metallic pin 120 due to the base 110 being exposed to a temperature of the softening point or higher. As shown in FIG. 13C-3, there is a problem in that the metallic pin 120 is exposed to the temperature of about 1000° C., an oxide film 180 grows around the metallic pin 120, and the electrode 130 is not electrically connected to the electronic component 140.